We evaluated febrile convulsions prospectively in 42 children to inves
tigate the association between acute human herpesvirus-6 (HHV-6) infec
tion and first-time febrile convulsions, using both virologic and sero
logic methods. Eight children had primary HHV-6 infection documented b
y viral culture and an additional three by acute- and convalescent-pha
se serologic studies. These findings indicate that acute HHV-6 infecti
on is a frequent cause of febrile convulsions in young children.